Polybutadiene rocket propellant compositions



United States Patent 3,249,475 POLYBUTADIENE ROCKET PROPELLANT COMPOSITIONS Joseph S. Jorczak, Hamilton Square, N.J., and John M.

This invention relates to new and useful improvements in rocket propellant compositions, and methods of preparing same.

Objects of the invention are: the provision of a rocket propellant composition having stable physical and chemical characteristics; the provision of a composition suitable for casting in a rocket case; the provision of a liquid or plastic composition that, following its introduction into the rocket case, may be subjected to a curing operation whereby there is effected a solidification or conversion of the composition into an elastomeric body having desirable combustion characteristics; the improvement in methods of preparing cast bodies of rocket propellant composition which involves casting the composite material directly in a rocket case and thereafter subjecting the material, in situ, to a heat curing operation to convert said material into an elastomeric body.

An important limitation on the availability of propellant compositions of matter suitable for loading in the motor compartments of rocket structures, consists in the susceptibility of the material to change in performance characteristics in response to ambient temperaure conditions. -In view of this consideration it has been a goal, to develop rocket propellant compositions that would be independent of varying conditions encountered in the field.

It is known to prepare rocket propellant compositions in the form of shaped bodies, and to this end the compositions may be pressed or extruded or otherwise prepared in definite shapes and sizes, and in this prepared condition, loaded in rocket casings.

This invention relates to improved compositions which are adapted to direct casting in the rocket shell; and further relates to the method of production of a cast body of propellant that is predominately elastomeric, and that remains so, over a range of' low temperatures, and to methods of casting and curing same.

According to the present invention it has been found possible to prepare homogeneous compositions having elastomeric properties, that satisfactorily retain their properties, even when subjected to low temperatures that Viscosity, Saybolt Furol Seconds at 100 F 1500 Ash, percent 0.62 Volatile matter A mm., 300 F., percent 0.39 Iodine number About 360 Color, Gardner scale 14 Specific gravity, 60/60 F. 0.9138

It was found upon investigation that this polymer could be converted to a rubbery material at 140 F. to 158 F.

An oxidizing agent is incorporated with the fuel material and for this purpose a compound containing available oxygen, may be used. Especially suitable are inorganic nitrates or perchlorates such as, ammonium nitrate, potassium perchlorate, or ammonium perchlorate. The oxidizing agents may be incorporated either as single compounds, or in the form of admixture of several oxygenyielding compounds.

Additional suitable materials may be incorporated in the composition, as, for example, lubricants, coloring agents, curing agents, or cure activators.

The following example illustrates a specific embodimentof a composition according to the invention:

An internal burning grain containing this fuel, having a six pointed star perforation, was cast directly into a rocket case. The rocket was cured for 72 hours at 158 F. The rocket case had been coated on the inside with an adhesive, and the end surfaces of the grain were coated with the same material.

The rocket was fired at K =350. It burned for 3.5 seconds at an average uncorrected chamber pressure of 285 p.s.i. with a maximum uncorrected chamber pressure of 305 p.s.i.

The example cited is not intended to restrict this invention to the stated proportions of components, or to the particular oxidizer used, or to the above combination of fuel, oxidizer, and chemicals useful in the conversion of the polymer to an elastomer. Other combinations of sulfur and rubber accelerators, and other proportions have been found that render feasible the conversion at higher and lower temperatures. The properties of the polymer listed above are descriptive only and are not intended to restrict the invention to this particular polymer. inside of the rocket case, and on the end surfaces of the grain, may consist of any material adapted to the purpose, and having suitable adhesive properties. Where propellant compositions involving constituents other than those specifically exemplified, are employed, the temperatures and times necessary for effectively curing the compositions, while generally within the limits above set forth, will be subject to adjustments that can be determined by experiment, for optimum results.

Having thus for purposes of illustration described an example of the invention it will be understood that same is not limited by the terms of description, but what we claim is:

1. A rocket propellen-t grain consisting essentially of a homogeneous elastomeric mixture in cured solid state of about 30% polybutadiene and about 66% of an oxidiz- The coating material used on the 3 4 3. A rocket propellant composition in cured solid 2,479,470 8/1949 Carr 52--.5 state containing the following ingredients in the follow- 2,479,828 '8/ 1949 Geckler. ing proportions: 2,539,404 1/ 1951 Crutchfield.

' Percent 2,563,265 8/1951 Parsons 52.5 X Ammonium perchlorate 65.900 5 Liquid polybutadiene 29.470 FOREIGN PATENTS Ste-mic i 0,295 437,228 2/ 1912 France. Zinc dibutyl dithioearbamate 1.474 17,994 1894 Great g g S lf 2 579,057 7/ 1946 Great Britain. C b bl k 0 9 10 655,585 7/1951 Great Britain.

References Cited by the Examiner UNITED STATES PATENTS 2,360,867 10 1944 Garvey. 2,468,027 4/1949 Britton et a1.

Examiners.

15 B. R. PADGETT, Assistant Examiner. 

1. A ROCKET PROPELLENT GRAIN CONSISTING ESSENTIALLY OF A HOMOGENEOUS ELASTOMERIC MIXTURE IN CURED SOLID STATE OF ABOUT 30% POLYBUTADIENE AND ABOUT 66% OF AN OXIDIZING AGENT SELECTED FROM THE GROUP CONSISTING OF INORGANIC SALTS OF NITRIC ACID, INORGANIC SALTS OF PERCHLORIC ACID, AND MIXTURES THEREOF. 